1. Field of the Invention
This invention relates to a single-use syringe, more particularly to a single-use syringe in which fluid-tightness of a barrel is disrupted when the syringe is displaced to a disposal position so as to render the syringe unreusable.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional single-use syringe is shown to include a barrel 11 which has an axially extending surrounding wall 113 defining front and rear passageways 112, 111, and a surrounding shoulder 114 disposed between the front and rear passageways 112, 111, a needle assembly 12 which is sleeved on a front opened end of the surrounding wall 113, a plunger 13 which is disposed to be movable in and along the rear passageway 111 and which has a tapered head 131 formed on a front end thereof, a deformable sealing member 14 which is retainingly sleeved on the tapered head 131, which is in fluid-tight and slidable engagement with the surrounding wall 113 at the rear passageway 111, and which has an axially extending vent hole 132 communicated with the ambient air, and a plug 15 which is detachably connected to the deformable sealing member 14 and which closes the vent hole 132. An inner surface of the surrounding wall 113 has a retaining ring 115 formed adjacent to the shoulder 114. The plug 15 has an anchoring portion 151 projecting forwardly and outwardly of the deformable sealing member 14 such that, subsequent to completion of injection, the deformable sealing member 14 is brought to abut against the shoulder 114 and the anchoring portion 151 is engaged with the retaining ring 115 to thereby permit disengagement of the plug 15 from the deformable sealing member 14 when the plunger 13 is pulled rearwardly, and to thereby disrupt the fluid-tightness of the vent hole 132 for rendering the syringe unreusable. However, when the anchoring portion 151 is forced to be engaged with the retaining ring 115, the frictional force between the plug 15 and the deformable sealing member 14 is increased, which may be greater than the force of engagement between the anchoring portion 151 and the retaining ring 115, thereby adversely affecting separation of the plug 15 from the deformable sealing member 14. Moreover, formation of the retaining ring 115 on the inner surface of the barrel 11 is inconvenient during manufacture.